(a) Field of the Invention
This invention relates to a filter provided, for example, for an internal combustion engine for a motor vehicle to filter oil circulating through the internal combustion engine, an oil strainer including the filter and a method for manufacturing the oil strainer.
(b) Description of the Related Art
Conventionally known oil strainers of such type include a strainer body formed in the overall shape of a cylinder and a filter disposed in the interior of the strainer body, as disclosed, for example, in Published Japanese Patent Application No. 2002-210310. The strainer body is formed by assembling resin-made first and second tubular members extending in an axial direction of the strainer body. The junctions of the first and second tubular members are fusion bonded. The first tubular member is formed with an oil inlet, while the second tubular member is formed with an oil outlet. Oil sucked through the oil inlet of the first tubular member into the strainer body is strained by passing through the filter and then flows out through the oil outlet of the second tubular member.
When two resin members are fusion bonded in the above manner, bonding flash is produced. An example of a solution to the production of bonding flash is disclosed in Published Japanese Patent Application No. 2002-248685. The document discloses that a bonding flash accommodation part for accommodating bonding flash produced upon fusion bonding of a cylindrical case and a cover for covering the opening of the case is provided closer to the case interior than the fusion bonding parts of the case and the cover. Thus, when bonding flash falls off from the fusion bonding parts owing to vibrations or impacts, it can be accommodated in the bonding flash accommodation part to prevent the bonding flash from falling down into the case.
In the technique disclosed in Published Japanese Patent Application No. 2002-248685, provision of bonding flash accommodation part is only at a position closer to the case interior than the fusion bonding parts, i.e., only on one side of the fusion bonding parts in an axial direction of the case. Therefore, if the technique disclosed in Published Japanese Patent Application No. 2002-248685 is applied to fusion bonding of the first and second tubular members constituting the oil strainer body disclosed in Published Japanese Patent Application No. 2002-210310 to form a bonding flash accommodation part, the formation of bonding flash accommodation part is only on one axial side of the fusion bonding parts of the first and second tubular members. Thus, bonding flash formed to extend from the other axial side of the fusion bonding parts of the first and second tubular members is believed to fall off from the fusion bonding parts and down into the oil reservoir space without being accommodated in the bonding flash accommodation part. If the oil strainer sucks in such bonding flash together with oil, the filter becomes more likely to be clogged.
A first aspect of the present invention has been made in view of this point and, therefore, its object is that even if bonding flash is produced to extend from both axial sides of the fusion bonding parts of the first and second tubular members in forming a strainer body by fusion bonding the first and second tubular members, the bonding flash is prevented from falling down from the strainer body, thereby preventing clogging of the filter.
Conventionally known filters of such kind are formed in the shape of a bottomed circular cylinder composed of a bottom wall and a peripheral wall, as disclosed, for example, in Published Japanese Utility-Model Application No. S60-31319. The bottom wall and the peripheral wall of the filter have straining screens formed therein and include a plurality of ribs for reinforcing the screens. The screens and ribs are integrally molded from a resin material, thereby providing reduced parts account.
When the screens and ribs are integrally molded from a resin material as disclosed in Published Japanese Utility-Model Application No. S60-31319, some of fluid flow holes forming the screens may be collapsed to provide a defective product. In order to prevent such a defective product from being shipped as it is, the filter after molded is subjected to a finished product inspection. However, since the fluid flow holes are very small, human visual inspection for the fluid flow holes is poor in inspection accuracy and takes much time. In view of this, there is a recent demand for a finished product inspection by image processing using a computer, which saves labor while enhancing the inspection accuracy and shortening the inspection time.
However, since the filter disclosed in Published Japanese Utility-Model Application No. S60-31319 has a circular cylindrical shape, its peripheral wall has a curved surface. Therefore, in inspecting the screen of the peripheral wall by image processing, the peripheral wall has a part close to the image pickup camera and a part far from it and, therefore, the camera cannot focus on the whole of the image pickup range. In other words, the range where the image pickup camera can take and inspect image at a time is limited to the narrow range where the image pickup camera can focus. Therefore, the peripheral wall can be inspected little by little, which takes a long time to inspect the whole area of the peripheral wall.
Furthermore, since the peripheral wall has a curved surface as described above, when it is picked up from one side by the image pickup camera, the fluid flow holes of the screen in front of the image pickup camera are imaged into different shapes from the fluid flow holes turned off from the front of the image pickup camera. If, thus, the shapes of the fluid flow holes picked up are different from portion to portion of the peripheral wall, this cannot provide accurate inspection results.
A second aspect of the present invention has been made in view of this point and, therefore, its object is that in inspecting the screen formed in the peripheral wall of the resin-made, bottomed cylindrical filter by image processing, a wide area can be accurately inspected at a time to provide a high-accuracy inspection result in a short time, thereby saving the filter cost.
Oil strainers disposed in oil pans are also known. Such an oil strainer is composed of a case formed in the overall shape of a linearly extending cylinder and a filter disposed in the interior of the case to strain oil, as disclosed, for example, in Published Japanese Patent Application No. 2002-210310. The case is formed by fusion bonding one ends of resin-made first and second tubular members. The end of the first tubular member opposite to the fusion bonding part is formed with an oil inlet, while the end of the second tubular member opposite to the fusion bonding part is formed with an oil outlet. Oil sucked through the oil inlet of the first tubular member into the oil pan is strained by passing through the filter, then flows out through the oil outlet of the second tubular member and is then used to lubricate various components.
The oil inlet of the oil strainer should be located at such a position in the oil pan as to surely reach the oil surface level in order to prevent bad oil suction into the oil pan. However, if the oil pan has a complicated shape or has an obstacle projecting towards the interior of the oil pan, such as a cylinder block, the linearly extending cylindrical oil strainer as in Published Japanese Patent Application No. 2002-210310 would make it difficult for the oil inlet to be located at a desired position while keeping off the obstacle. To cope with this, it can be considered to bend the case of the oil strainer. However, in this case, the tubular member forming part of the case must be bent and, therefore, an undercut will be formed upon molding. This complicates the structure of a mold for molding the tubular member and in turn increases the production cost of the oil strainer.
A third aspect of the present invention has been made in view of this point and, therefore, its object is to provide an oil strainer which includes a case formed by assembling a plurality of tubular members, can reduce the production cost by making the structures of molds for molding the tubular members as simple as possible and concurrently can locate the oil inlet at a desired position by forming a bent portion of the case.